1. Field of the Invention
The present invention relates to techniques for enhancing digital images. More specifically, the present invention relates to a technique for enhancing clarity of an image by increasing the color contrast across object boundaries in the image.
2. Related Art
In many situations it is desirable to zoom into a portion of a digital image to view the portion in more detail. During a digital zoom operation, new pixels are typically added between existing pixels, and color values for these new pixels are interpolated from the color values of the surrounding pixels in the original image. However, pixel interpolation is an approximation process, so the image loses quality each time an interpolation operation is performed. In particular, pixel interpolation blurs object boundaries. This is because pixel interpolation averages color values of the surrounding pixels to obtain color values for a new pixel. As a result, high-contrast transitions of color values on or near object boundaries in the original image are rendered into more gradual transitions with lower contrast.
This boundary blurring can significantly degrade image quality, which can reduce viewing satisfaction, and can cause an unpleasant visual experience. Furthermore, in many cases, users want to edit zoomed-in versions of the original images. Unfortunately, the blurred boundaries can seriously degrade the precision of such user-editing operations. Hence, it is desirable to sharpen the blurred boundaries if possible to enhance overall clarity of the images and to facilitate user-editing operations.
Hence what is needed is a method and an apparatus for enhancing boundary sharpness without the above-described problems.